Gandalf wins, since he is one of the god-like Maiar and therefore is pretty much OP against anyone else who isn't a Maiar or above (Saruman, Sauron, and the Balrog were all Maiar as well).

So it goes pretty much like this. 

"Hey, i'm Gandalf. The darkness will not avail you!"

"Vat?"

*Chop*